1. Field of the Invention
In general, the present invention relates to road construction. More particularly, the present invention relates to a new and improved system and method for providing a superior level road construction using asphalt and paving machines by utilizing a laser guide system. It is understood that the invention is not limited to a specific road construction utilization.
2. Description of the Prior Art
It is obviously desirable to provide a smooth and level surface in the construction of a road. Furthermore, the Department of Transportation imposes pavement and bridge deck smoothness on many of their projects and may utilize a profilograph to determine the smoothness of the paving on a project. A project is often divided up into 525-foot long segments called extents. By example, under the Oklahoma provision, an unacceptable bump is defined as a vertical deviation greater than 0.60 inches in a 25-foot span.
An unacceptable bump is required to be corrected by grinding until it is within tolerance at no additional charge to the Department. Not only does the contractor have to pay to correct the problem, the Department will also penalize the contractor by means of pay reduction for that extent. Pay reduction can be up to $7,500 per extent. By example, a four-lane highway project that is eight miles long typically has 320 extents. If a maximum penalty is imposed, the pay reduction could be $2,400,000 and further include the costs incurred by the contractor to correct any bumps in excess of the 0.60 inch per 25 foot span. Still furthermore, the Department may pay a bonus for any extent that is exceptionally smooth. This bonus can be up to $1,250 per extent. The example of the same four-lane highway above that is eight miles long could have a maximum bonus of $400,000.
In asphalt road construction, a paving machine and or paver is essentially comprised of three main parts. First is the tractor that propels the machine down the road. Second is the internal machinery that generally accepts the asphalt into a hopper from a separate supply truck and moves it to the rear of the paver via conveyors and augers. The third is the screed that is attached to the towing side arm and pulled behind the paver to smooth and control the thickness of the asphalt being laid. The screed is comprised of a large flat piece of steel plate that has adjustable pitch to control thickness. When in pave mode, there is no mechanical means of raising or lowering the screed to increase or decrease paving thickness. The screed is in a free-floating mode as it is drug across the surface of the asphalt, so the only way to control the thickness of the mat is by increasing or decreasing the pitch of the screed plate.
The screed setting generally determines the level and or plane of the road and the system typically works very well once the paving process is underway, but is known to be difficult to get the screed setting right for the initial takeoff. The term “takeoff” generally refers to the operation of the start of a section to be paved that starts anew from a previous section that has already been paved. By example, to begin each day's new run, the paver is backed up to where the previous day's run had ended and the asphalt stopped. Takeoff boards or spacers are placed on top of the previous day's asphalt and then the screed is set down on top of these spacers. These spacers are essential due to the fact that the new asphalt passing under the screed is not yet compacted. Compaction will occur when a separate machine called a roller passes over the freshly laid asphalt at which time the thickness of the mat of asphalt will decrease.
The spacers must be the proper thickness to allow for the new asphalt to be compacted to the same thickness of the previous days run. Once the screed has been set down on the spacers, the screed operators have to first adjust the screed pitch to make it set flat on these spacers, which is often referred to as “nulling” the screed. The screed pitch is then increased to allow the screed to lay the new asphalt in the exact same plane as the previous day's run.
This is the difficult part. There is no way to gauge how much pitch is needed to achieve the perfect takeoff. There are many variables that determine the amount of pitch required such as mat thickness, type of mix being laid, mix temperature, screed temperature, and mat width are just a few. A reason it is so important to achieve a perfect takeoff is because the penalty of unacceptable bumps and the reward for proper leveling as well as the generally desirable smooth and level construction.
The current method for executing a proper takeoff is to use some sort of measuring device, usually a threaded rod with a nut set at the proper thickness, to poke into the newly laid mat to gauge thickness. Although this gives an accurate measurement, it is measuring behind the screed after the pavement has been laid. By the time it is realized there is a need for a correction, the mat is already out of tolerance and the ride has been compromised.
What is needed is a real time measurement before and during takeoff at the exact point where the material is passing under the screed and connecting to the previously laid asphalt. Of note, the invention is not necessarily directed strictly to asphalt road applications and the used terminology should not be considered limiting the invention to such. Likewise, the current invention is not limited to road applications per se. It is further understood and contemplated that the current invention may be used in association with other applications and utilities.
The current industry is constantly looking for effective, durable, and cost effective construction systems and methods for implementation of same. Thus, there is a need for a new and improved, apparatus, system and method of use as outlined. The current invention provides a solution where the prior art fails.